[JumpThreading] NFC: Don't cache F.hasProfileData()

Summary:
With this patch, we no longer cache F.hasProfileData().  We simply
call the function again.

I'm doing this because:

- JumpThreadingPass also has a member variable named HasProfileData,
  which is very confusing,

- the function is very lightweight, and

- this patch makes JumpThreading::runOnFunction more consistent with
  JumpThreadingPass::run.

Subscribers: hiraditya, jfb, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70602